Question

我正在尝试捕获照片并在Xamarin中显示所捕获的图像，但是更改图像源绑定似乎不起作用。这似乎真的很简单，所以我不确定我要去哪里。

MainPageViewModel.cs

public class MainPageViewModel : ViewModelBase
{

    private string _imageSource;
    public string ImageSource
    {
        get { return _imageSource; }
        set
        {
            _imageSource = value;
            SetProperty(ref _imageSource, value);
        }
    }

    public DelegateCommand TakePhotoCommand { get; private set; }

    public MainPageViewModel(INavigationService navigationService, IPageDialogService pageDialogService)
        : base(navigationService)
    {
        Title = "Main Page";

        _dialogService = pageDialogService;

        TakePhotoCommand = new DelegateCommand(TakePhoto);

    }


    async void TakePhoto()
    {

        await CrossMedia.Current.Initialize();

        if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
        {
            await _dialogService.DisplayAlertAsync("No Camera", ":( No camera avaialble.", "OK");

            return;
        }


        var file = await CrossMedia.Current.TakePhotoAsync(new Plugin.Media.Abstractions.StoreCameraMediaOptions
        {
            PhotoSize = Plugin.Media.Abstractions.PhotoSize.Medium,
            Directory = "Sample",
            Name = "test.jpg"
        });

        if (file == null)
            return;

        // This does get called ok
        ImageSource = file.Path;

    }
}

ViewModelBase.cs

public class ViewModelBase : BindableBase, INavigationAware, IDestructible
{
    protected INavigationService NavigationService { get; private set; }

    private string _title;
    public string Title
    {
        get { return _title; }
        set { SetProperty(ref _title, value); }
    }

    public ViewModelBase(INavigationService navigationService)
    {
        NavigationService = navigationService;
    }

    public virtual void OnNavigatedFrom(NavigationParameters parameters)
    {

    }

    public virtual void OnNavigatedTo(NavigationParameters parameters)
    {

    }

    public virtual void OnNavigatingTo(NavigationParameters parameters)
    {

    }

    public virtual void Destroy()
    {

    }
}

MainPage.xaml

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="PhotoTesting.Views.MainPage"
             Title="{Binding Title}">

    <StackLayout HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand">
        <Image Source="{Binding ImageSource}" WidthRequest="200" HeightRequest="200" Aspect="AspectFill" />
        <Button x:Name="CameraButton" Text="Take Photo" Command="{Binding TakePhotoCommand}" />
    </StackLayout>

</ContentPage>

我知道图像捕获位工作正常，问题似乎只是在页面加载后设置image.source。

Answer 1

您需要将 Image 的 Source 属性绑定到 ImageSource < / em> 在MainPage.xaml中
可以从文件流中获取 ImageSource 对象。这是代码：

public class MainPageViewModel : ViewModelBase { private ImageSource _imageSource; public ImageSource ImageSource { get { return _imageSource; } set { _imageSource = value; SetProperty(ref _imageSource, value); } } public DelegateCommand TakePhotoCommand { get; private set; } public MainPageViewModel(INavigationService navigationService, IPageDialogService pageDialogService) : base(navigationService) { Title = "Main Page"; _dialogService = pageDialogService; TakePhotoCommand = new DelegateCommand(TakePhoto); } async void TakePhoto() { await CrossMedia.Current.Initialize(); if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported) { await _dialogService.DisplayAlertAsync("No Camera", ":( No camera avaialble.", "OK"); return; } var file = await CrossMedia.Current.TakePhotoAsync(new Plugin.Media.Abstractions.StoreCameraMediaOptions { PhotoSize = Plugin.Media.Abstractions.PhotoSize.Medium, Directory = "Sample", Name = "test.jpg" }); if (file == null) return; // Here is the problem //ImageSource = file.Path; // This is the fix ImageSource = ImageSource.FromStream(() => file.GetStream()); } }

在Xamarin中使用MVVM捕获和更新图像源

1 个答案: